"Earlier tonight we experienced an issue with our weight reporting system, which caused system wide flight delays," the airline said in a statement on its Twitter feed late on Thursday in the United States.
"We have resolved the issue and are working to get customers to their destinations as soon as possible. We apologize for the inconvenience."
Passengers said they had been forced to wait on board planes or inside terminals as flights were delayed for several hours."On the plane for more than an hour, away from the gate and no communication. What's happening?," one passenger tweeted.
As of 9:20 AM EDT (13:20 GMT), United had cancelled 10 flights and delayed 37, or 1 percent of its operation, according to flight tracking website FlightAware.com. Many travelers were impacted, however, given that issues occurring overnight often impact a U.S. airline's flights coming from outside the country on bigger planes.
In Paris, passengers complained as check-in lines grew for a flight to New York, a Reuters reporter said on Friday morning.The airline said the problem had been resolved as of 3 a.m. eastern time (0700 GMT) on Friday.
It is the third computer glitch to recently hit United's owner United Continental Holdings and the latest in a series of problems that have tested the reliance on technology of some of the world's largest carriers.
This has prompted some experts to question whether the airline industry has invested enough in technology infrastructure, given new profits from baggage and cancellation fees.
On June 2, 2015 software needed to dispatch United's flight plan briefly lost functionality.In July 2015, the same airline's flights were disrupted after a computer problem blocked access to reservations records.
This August, Delta Air Lines cancelled thousands of flights and delayed many others after a power outage hit its computer systems.
And in September, a system-wide computer problem at British Airways caused significant delays.After the two previous incidents, United said it had invested in backup plans.